The dos and don’ts of genset maintenance

Growing risks worldwide make backup power more crucial than ever

Credit: MTU Onsite Energy

A standby power system is only as reliable as those responsible for operating and maintaining it. Proper maintenance is as critical as the unit itself, writes Tyson Robinett

It’s your worst nightmare: the power goes off and stays off.

A utility outage can be disastrous for any business, often arriving unexpectedly and occurring at the worst possible moment. Although the majority of utility outages tend to be infrequent and of short duration, catastrophic losses can occur if electrical power from the utility is lost, even for a short time.

Around the world, major power failures are occurring more frequently. This is due, in part, to the world’s increasing demand on electrical grids, but Mother Nature also plays a major role. Research shows that the number of weather-related incidents has increased worldwide during the past 40 years. In fact, as I write this, Hurricane Joaquin left destruction in its path as the Category 4 storm hammered parts of the Bahamas and Bermuda and brought record-breaking flooding to South Carolina. Crews throughout the Caribbean and the US east coast are scrambling to restore power or to brace for what may come.

There will always be an amount of uncertainty when it comes to utility outages, but there are ways to reduce risk. Businesses around the world are producing their own emergency power during outages with the help of on-site diesel-powered backup generator sets. However, just having a generator is not enough.

A standby power system is only as reliable as those responsible for operating and maintaining it. Proper maintenance is as critical as the unit itself and can be the difference in having the lights needed to perform emergency surgery in a critical moment, or powering airport terminals on a stormy winter day.

To ensure that your emergency power system is operable when most needed, this guide addresses a few key do’s and don’ts to ensure that your generator set remains operable in the event of an outage.

DO: Plan maintenance

It may seem obvious, but establishing a maintenance schedule is paramount to generator reliability. Planned maintenance programmes ensure emergency standby power systems remain in a constant state of readiness. Planned maintenance also ensures proper system performance, while preventing the risk of safety hazards for onsite personnel.

It’s important to establish a maintenance schedule that is based on the specific power application and the severity of the environment. For example, if the generator set is located in an extremely cold or hot climate, or is exposed to salt air, the system may require special needs, such as maintenance and inspection in more frequent intervals.

When undertaking this task, large facilities should engage their local generator set distributor to provide support in creating a plan customised to the exact needs of the facility. Working with a distributor also ensures that the maintenance is completed on a regular schedule with full documentation and according to the manufacturer’s recommendations.

A preventative maintenance plan should include the following:

ࢀ¢ Inspections;

ࢀ¢ Oil changes;

ࢀ¢ Cooling system service;

ࢀ¢ Fuel system service;

ࢀ¢ Testing starting batteries;

ࢀ¢ Regular engine exercise under load;

ࢀ¢ Documentation tracking what’s been done.

The best maintenance plans include more than the engine generator. The entire power distribution system should be considered. For example, the switchgear should be cleaned, calibrated and scanned. Additional preventative maintenance should also be performed according to industry codes and standards.

DO: Train personnel

Once you have a maintenance schedule in place, adhere to it by conducting the required service and testing. Regular maintenance and periodic testing is required by code in mission-critical applications. Only properly trained service technicians should do this. For facilities with on-site service technicians, operator training and testing is not optional. Untrained and inexperienced technicians often overlook incremental failures that can lead to large system malfunctions.

Personnel training begins during the commissioning process and should cover system operation, record-keeping and periodic maintenance. Operators must also be familiar with all the power system components, alarm conditions, and operation and maintenance procedures. Special attention should be given to critical subsystems such as fuel storage and delivery, starting batteries, engine coolant heaters, and airflow in and out of the generator building or enclosure. Frequent retraining is also necessary, along with making sure that personnel maintain an operational history of the power system.

A trained technician performing maintenance

Credit: Central Power Systems & Services

Genset manufacturers and distributor service technicians are available to help and, at a minimum, should work alongside on-site service managers, as they are usually the most qualified. Distributor service technicians, in addition to being trained on the equipment, follow the maintenance procedures as recommended for standby generator systems by bodies such as NFPA, NEMA and EGSA. Most will also carry with them the necessary replacement parts, oil and fuel.

DO: Test under real-world conditions

At least once a year, facilities should exercise the power system under the actual facility load and full-emergency conditions to verify that the system will start, run and accept the rated load. Running for up to several hours under these conditions helps to test all the system components. When operated with the actual building load, the entire power system should be tested, including the automatic transfer switches and switchgear.

Resistive load bank testing is the most common way of testing a generator set to its full nameplate rating. Without any interruption to the building, this test will help identify any possible weaknesses under controlled conditions that would lead to overheating or shutting down. Running a resistive load bank test with an artificial load should take no longer than eight hours unless there are government and military specifications, which may require up to 24 hours for testing.

Technicians will carry the necessary replacement parts, oil and fuel

Credit: Central Power Systems & Services

Reactive load bank testing is another method which allows for proper calibration of load sharing and voltage-regulating systems in parallel operation installations. However, it is usually only used for new installations with critical large motor loads to ensure the generator will not deteriorate or change once tested and proven at startup.

Regular testing and systems monitoring can be the difference between a generator starting during an emergency and one stalling out. Besides verifying that the generator set will start and run, periodic exercise has the benefit of heating up diesel fuel and eliminating accumulated condensation in the fuel tank. Since clogged fuel filters and fuel contamination are among the leading causes of power system malfunctions, the cycling and refreshing of fuel is an important step in ensuring overall system reliability.

DON’T: Ignore fuel storage

Standby generator systems are more susceptible to fuel contamination because the fuel sits idle and unused for long periods. If left untreated, fuel will substantially degrade. Fuel supplies should be replenished regularly to ensure reliable starting and to prevent clogged fuel filters. In addition, fuel quality should be tested often. Primary types of degradation include:

ࢀ¢ Water contamination Water builds up from condensation on the interior walls and on top of the fuel tank. This occurs almost every day when the outdoor temperature increases faster than the temperature inside the fuel and tank.

ࢀ¢ Microbial organisms Microbes are always present in diesel fuel. Too many will prematurely clog filters, which will not be evident until the engine must pull full load.

ࢀ¢ Gelling Diesel fuel freezes at a much higher temperature than most other fuels. Standard diesel can freeze at any temperature below 0à‚°C, which will lead to gelling and clogged fuel pipelines.

ࢀ¢ Degradation Diesel fuel starts to degrade after six months and can render fuel completely useless after two years. Additives, fuel filtering, regular sampling and diesel fuel supplements help prevent or remove contaminants that can lead to degraded fuel and significant engine damage.

DON’T: Ignore the battery

Maintenance of a generator set’s starter battery is critical to ensuring sufficient ampere capacity to start the engine. Nearly 50% of emergency genset failures are attributed to weak starting batteries. As a preventative measure, replace batteries every two years.

During maintenance checks, trained technicians should carry out the following tests to ensure batteries are meeting required specifications:

ࢀ¢ Specific gravity Test the battery’s Specific Gravity level with a hydrometer and compare the levels with the battery supplier. Before beginning testing, ensure that the battery is rested with no charge or discharge for 24 hours.

ࢀ¢ Equalise charge Although equalising charging isn’t recommended to be used routinely, there should be occasional checks to ensure that every plate in each cell reaches a full state of charge in their respective positions.

ࢀ¢ Battery capacity testing Ensure that the battery is fully charged initially. Next, use a resistive battery tester to place a load of 5% of battery capacity to measure the battery’s handle.

ࢀ¢ Visual check for corrosion and dirt Dirt can block current flow in connectors and cause resistance between terminals. Clean dirty or corroded terminals and connectors with a wire brush dipped in a solution of baking soda and water. After cleaning, rinse with clean water and coat terminals with a thin coat of petroleum jelly or a corrosion inhibitor.

Electrolyte level checks are also important. If fluid levels in battery cells drop below the top level of the separator, add distilled water to cover the plates. Lastly, if leakages are found due to a cracked battery casing or spilled electrolyte, replace the entire battery.

Standby generator sets are reliable systems with normal availability in excess of 98% on an annual basis. To get the highest reliability, facilities should take great care to plan and employ frequent maintenance and testing. When done in close co-ordination with a local distributor and the factory, this co-ordination can help identify potential failure modes, develop solutions before problems occur and decrease downtime. By considering the factors outlined above, managers of mission-critical facilities can be assured that they will never be left in the dark.

Tyson Robinett is general manager in the air, light and power generation division at Central Power Systems & Services

This article is available on-line. Please visit

No posts to display